Computer Simulation Of Microstrip Line Filters And Electromagnetic Band Gap Structures

Microstrip line filters have some advantages such as small size, lightweight, broad frequency band, easy to form and so on, but it still owns shortcomings, such as high loss, power limitation, and so on. One of the principal characters of microwave line filters is that its geometric size is comparable to the relevant wavelength. When wavelength varies, microwave filter is inevitable to behave the periodic character.Simulation in this paper by FDTD and FEM based on frequency domain are presented to simulate microstrip line structures. On the basis of those, microstrip line filters like microstrip line low pass, band stop, band pass filters are simulated to achieve some important parameters, such as frequency bandwidth, correspondence of stop band. By comparison of measured data with the theoretic analysis and the simulated data, the feasibility of using those software to simulate microstrip line filters are discussed. In this thesis, the problems such as defining model, defining stimulation, computational time and others which exist in solving those problems in stimulating microstrip such as the difficulties in defining models, the difficulties in defining stimulation, inefficient computation and so on are described. What the thesis has done can guide the engineering design to some extent.Up to now, FDTD has the advantages in simulation, such as computation once in time domain to replace many times computation in frequency domain. However, low precise and efficiency are shortcomings of FDTD method. FDTD has the distinct advantages in simulating micriostrip PBG structure in timedomain. While FEM adopt adaptive gridding mesh and sub-gridding technology, it is easily to deal with complicate structure and inhomogeneous medium. FEM has the advantages like more accurate simulating and higher computation efficiency. So FEM has higher engineering prospect.Due to their unique frequency selective characteristics and small compact and easily to do PCB board, EBG structures are introduced. The traditional EBG filters, also called photonic bandgap filters, are periodic structures in the floor or in the dielectric capable of prohibiting the propagation of electromagnetic waves within a certain band of frequencies. So the EBG structure is proposed, simulated and measured to get wide stopband to overcome the periodic accessory correspondence. A good agreement between the simulated and measured results was achieved. The PV-EBG is simulated to get narrow stopband. The EBG structures have lower loss and higher Q than normal microstrip filters, so they are suitable for filters.